A major segment of psychopathology consists of symptoms formed in response to stress. Psychotherapeutic treatment and prophylaxis could be improved if we knew more about how the stress event factors and personality factors interrelate in terms of typical cognitive and affective responses. This research consists of experimental studies of cognitive response to stress. The compulsive repetitions of trauma frequently observed in traumatic neuroses led us to predict intrusive and repetitive thinking as a typical cognitive response to stress. Mental contents of subjects are sampled in baseline conditions and after seeing neutral and stress films. The data has supported our prediction and indicated the potential utility of our methods. We are now investigating further the relationship between stress events and intrusive and repetitive thinking. We are studying the ways in which subjective experiences vary with alterations in the quantities and qualities of stress events, and the validity of our measure of intrusive thinking. We plan to investigate individual variations in the responsive tendency. If our predictions are supported by experimental evidence, we plan to use intrusive thinking as an index of cognitive stress and to examine the adaptational effects of various cognitive modes of stress response or stress preparation. Bibliographic references: Horowitz, M.J. Microanalysis of working through in psychotherapy. American Journal of Psychiatry, 131:11, 1208- 1212,1974; Horowitz, M.J. Stress response syndromes: Character style and brief psychotherapy. Archives of General Psychiatry, 31:768-781, 1974.